<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #flex-container{
            display: flex;
            flex-wrap: nowrap;
            height: 200px;
            background-color: lightblue;
            /*justify-content: center; 使项目在容器中居中*/
            justify-content: space-between;
            align-items: center;
            /*垂直对齐*/
        }
        #flex-container > div {
            background-color: #f1f1f1;
            width: 100px;
            margin: 10px;
            text-align: center;
            line-height: 75px;
            font-size: 30px;
        }
    </style>
</head>
<body>
<div id="flex-container">
    <div>1</div>
    <div>2</div>
    <div>3</div>
<!--    <div>4</div>-->
<!--    <div>5</div>-->
<!--    <div>6</div>-->
<!--    <div>7</div>-->
<!--    <div>8</div>-->
<!--    <div>9</div>-->
<!--    <div>10</div>-->
<!--    <div>11</div>-->
<!--    <div>12</div>-->
</div>
</body>
</html>